The conventional industrial method for preparing 2,4,5-trichlorophenol (TCP) involves the reaction of 1,2,4,5-tetrachlorobenzene with methanolic or aqueous, methanolic sodium hydroxide at high temperatures (ca. 180.degree. C. to 190.degree. C.). The disadvantage of such a process is that the combination of high temperature and alkalinity result in the formation of small amounts of 2,3,7,8-tetrachlorobenzodioxin (TCDD), one of the most toxic chemicals known. Even under the most stringent conditions, levels of 100 ppb or higher of TCDD may be formed and be present in the TCP. The presence of TCDD produced in the manufacture of TCP has been a major environmental concern and has virtually led to the non-use of the herbicide known as 2,4,5-T, a derivative of TCP.
If the benefits provided by the many useful products made from TCP are to continue to be produced there is a need for a process which provides TCP which is essentially free of TCDD (i.e. no TCDD is detectable by analytical tests that are sensitive to 1 part per billion). This invention provides such a process.